import sys
sys.set_int_max_str_digits(0)
N = int(input())
S = input()

ans = 0
for i, s in enumerate(S):
    if s == 'M':
        for j in range(1, N):
            if 0 <= i - j and i + j < N:
                l, r = S[i - j], S[i + j]
                if l == 'U' and r == 'G':
                    ans += 1
            else:
                break
print(ans)